December 2007, to be published in Physical Review D1


Are there approximate relations among transverse momentum dependent distribution functions?
H. Avakian, A. V. Efremov, K. Goeke, A. Metz, P. Schweitzer, and T. Teckentrup

Certain {\sl exact} relations among transverse momentum dependent parton distribution functions due to QCD equations of motion turn into {\sl approximate} ones upon the neglect of pure twist-3 terms. On the basis of available data from HERMES we test the practical usefulness of one such ``Wandzura-Wilczek-type approximation'', namely of that connecting $h_{1L}^{\perp(1)a}(x)$ to $h_L^a(x)$, and discuss how it can be further tested by future CLAS and COMPASS data.

© 2008 The American Physical Society.